The present application is based on and claims priority from Japanese Patent Application Hei 11-224335 filed on Aug. 6, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine and, particularly, a stator core of a rotary electric machine, which is useful to a vehicle AC generator.
2. Description of the Related Art
Recently, engine idling speed, car weight, and engine compartment space have been reduced. The engine idling speed has been reduced to improve environmental quality, the car weight has been reduced to improve fuel consumption, and the engine compartment space has been reduced to provide wider passenger compartment space. As a result, the size of an AC generator has been required to be smaller and more powerful.
WO/98/54823 proposes a vehicle AC generator which meets the requirement. Such a generator has a pair of conductor segments inserted into a plurality of slots, each connection end of which is connected to another to form a stator winding. This provides a stator winding of a high space factor and a low resistance.
In the above AC generator, each connection end of the conductor segments has a circumferentially and radially swelling vestige or lump, which congeals after each connection end was welded to form a stator winding. The vestige is formed because a melted portion tends to become spherical due to a surface tension. This reduces the distance between the circumferentially adjacent connection ends, which may cause insulation failure in the AC generator.
If the circumferential distance is so small that the distance is filled with resinous material. This prevents cooling air from passing between connection ends, resulting in reduction in the cooling performance. If the cooling air is interrupted, it is also difficult to remove electrolyte or foreign particles by air.
The present invention has been made to solve the above problems and to provide a rotary electric machine having a plurality of conductor segments which has improved insulation and cooling performances at the connection ends and a method of manufacturing the same.
In a method of manufacturing a rotary electric machine having a plurality of conductor segments according to the invention, each connection end is driven in the same circumferential direction until the connection end becomes solid. Accordingly, a vestige of the connection ends can be formed to swell in the same circumferential direction, and the circumferential size thereof can be made small. This increases the circumference distance between the circumferentially adjacent connection ends.
If the connection ends are not driven in the same circumferential direction, the melted portions become spherical due to the surface tension thereof at the connection ends to swell from the original periphery in opposite circumferential directions.
According to a feature of the invention, the welded portions are driven in the same circumferential direction so that the melted and swelling portions can move in the same circumferential direction. At this stage, the swelling amount is restrained by the surface tension, and the driven melted portion has more rectangular shape viewed in the axial direction. As a result, the circumferential size of the connecting ends having the congealed portions or vestiges is reduced. In other words, the circumferential distance between the adjacent connection ends can be increased. The melted portions are congealed while the connection ends are moved relative to a welding arc in a circumferential direction. The melted portions move to follow the welding arc as if the melted portions are driven or pulled by the welding arc. The melted portion can be formed by non-contact heating technology, which includes arc discharge, irradiation of a heat beam, such as a laser beam.
According to another feature of the invention, a magnetic field is applied to the welded portions while arc current is supplied thereto to drive the connection ends by an electro-magnetic force.